High-performance 2-to-4 decoder using nonlinear ring resonators in photonic crystal platform

In this research, a new photonic crystal structure for decoding operation with two inputs and four outputs is introduced. A square array of 28 × 45 silicon rods with a lattice constant of 485 nm has been used as the fundamental structure. Two input signals along with a bias signal reach the four output ports via nine waveguides. Four ring resonators are responsible for coupling light to the output ports. In each ring, a 4 × 4 array of nonlinear rods made of doped glass is used. Depending on the light intensity applied to the rings, one of the resonators couples the signal to one of the output ports. The use of ring resonators increases the coupling efficiency and enhances the light intensity at the output ports. As a result, the structure’s contrast ratio reaches 13.71 dB, and distinguishing between logic 0 and logic 1 for digital applications is well feasible. Calculation of the field components shows that its time response is 194 fs, faster than other structures. This attractive feature allows the designed decoder to be implemented in photonic circuits. Furthermore, the structure area is 296 µm² which is smaller compared to ring-based 2-to-4 decoders. Based on the obtained results, it can be said that the presented structure performs better compared to other photonic crystal-based decoders.